We wizards are not violent- but just to get an idea. A world war, as it is commonly understood, is a large-scale war involving many of the countries of the world or many of the most powerful and populous ones. World wars span multiple countries on multiple continents, with battles fought in many theaters. While a variety of global conflicts have been subjectively deemed "world wars", such as the Cold War and the War on Terror, the term is widely and generally accepted only as it is retrospectively applied to two major international conflicts that occurred during the 20th century: World War I (1914–1918) and World War II (1939–1945). In terms of human technological history, the scale of the two "world wars" was enabled by the technological advances of the second industrial revolution and the resulting globalization that allowed global power projection and mass production of military hardware, but wars on such a scale have not been repeated because of the onset of the Atomic Age and the resulting danger of mutually-assured destruction. It had been recognized that the complex system of opposing alliances (the German, Austro-Hungarian, and Ottoman Empires against the British, Russian, and French Empires was likely to lead to a worldwide conflict if a war broke out. Due to this fact, a very minute conflict between two countries had the potential to set off a domino effect of alliances, triggering a world war. The fact that the powers involved had large overseas empires virtually guaranteed that such a war would be worldwide, as the colonies' resources would be a crucial strategic factor. The same strategic considerations also ensured that the combatants would strike at each other's colonies, thus spreading the wars far more widely than those of pre-Colombian times.
War crimes were perpetrated in both world wars. Chemical weapons were used in the First World War despite the Hague Conventions of 1899 and 1907 having outlawed the use of such weapons in warfare. The Ottoman Empire has been considered responsible for the Armenian genocide, the death of over one million Armenians during the First World War.
The Second World War is the only conflict in which atomic bombs have been used. Hiroshima and Nagasaki, in Japan, were devastated by atomic bombs dropped by the United States. Nazi Germany was responsible for genocides, most notably the Holocaust, the killing of six million Jews. The United States, the Union of Soviet Socialist Republics, and Canada deported and interned minority groups within their own borders, and largely because of the conflict, many ethnic Germans were later expelled from Eastern Europe. Japan was responsible for attacking neutral nations without a declaration of war, such as the bombing of Pearl Harbor. It is also known for its brutal treatment and killing of Allied prisoners of war and the inhabitants of Asia. It also used Asians as forced laborers and was responsible for the Rape of Nanking where 250,000 civilians in the city were brutally murdered by Japanese troops. Non-combatants suffered at least as badly as or worse than combatants, and the distinction between combatants and non-combatants was often blurred by belligerents of total war in both conflicts.
The outcome of the world wars had a profound effect on the course of world history. The old European empires either collapsed or were dismantled as a direct result of the wars' crushing costs and, in some cases, their fall was due to the defeat of imperial powers. The United States became firmly established as the dominant global superpower, along with its ideological foe, the Union of Soviet Socialist Republics, in close competition. The two superpowers exerted political influence over most of the world's nation-states for decades after the end of the Second World War. The modern international security, economic, and diplomatic system was created in the aftermath of the wars.
Institutions such as the United Nations were established to collectivize international affairs, with the explicit goal of preventing another outbreak of general war. The wars had also greatly changed the course of daily life. Technologies developed during wartime had a profound effect on peacetime life as well, such as by advances in jet aircraft, penicillin, nuclear energy, and electronic computers. Since the atomic bombings of Hiroshima and Nagasaki during the Second World War, there has been a widespread and prolonged fear of a potential Third World War between nuclear-armed powers. The Third World War is generally considered a successor to the Second World War and is often suggested to become a nuclear war, devastating in nature and likely much more violent than the First World War and the Second World War combined; in 1947, Albert Einstein commented that "I know not with what weapons World War III will be fought, but World War IV will be fought with sticks and stones." It has been anticipated and planned for by military and civil authorities and has been explored in fiction in many countries. Concepts have ranged from purely-conventional scenarios, to limited use of nuclear weapons, to the complete destruction of the planet's surface. World War I (WWI or WW1), also known as the First World War, the Great War, or the War to End All Wars, was a global war originating in Europe that lasted from 28 July 1914 to 11 November 1918. More than 70 million military personnel, including 60 million Europeans, were mobilised in one of the largest wars in history. Over nine million combatants and seven million civilians died as a result of the war (including the victims of a number of genocides), a casualty rate exacerbated by the belligerents' technological and industrial sophistication, and the tactical stalemate caused by gruelling trench warfare. It was one of the deadliest conflicts in history, and paved the way for major political changes, including revolutions in many of the nations involved. Unresolved rivalries still extant at the end of the conflict contributed to the start of the Second World War only twenty-one years later.[ See? Muggles are so terrible...